MICKEY MOUSE-the ears on the head-some use M hands at the ears, some use 5-claw on head, representing ears
SPIDERMAN-SPIDER+MAN
BATMAN-BAT+MAN

Mickey- I've always seen the 5-claw on the head (one handed, usually)
Spidey- We use the upside down ILY hand to show the spinning or throwing of the web (with a little bit of attitude like a crime fighter, I guess!)
Batman- I've never used this with my son, but my husband and I would just fingerspell it. I guess BAT MAN is fine, and context will help.